MATLAB: Area Under Curve (or Between Curve)

areaarea under curve

How to find area under curve, I try trapz, not working.

sample=data(:,2); w=data(:,3); z=13.2 plot(sample, w, sample, z); area(w,z)

how to calculate area of shaded region?

I understand the time reference is in sample=data(:,2)

the function to integrate is in w=data(:,3) correct?

and the z=13.2 is some kind of squelch you want to remove while integrating? there is no need to plot 2 functions.

The area you are looking for is trapz(sample,w)

you have assigned z a scalar, but it should match the length of the data to integrate.

The integration goes from around 15 to 250, so the reference vector is tref=[15:1:250]

if you really want to remove those 13.2 (volts?) while integrating, this DC is actually

13.2*ones(1,length(tref)) so if you want to use two trapz, then

 trapz(sample,w)-z*ones(1,length(tref))

does it make sense?

regards

John

You just need one for loop as trapz operates also on matrices. This is the piece of code:

A = rand(32);
B = zeros(32);
for c = 1:size(A,2)
    B(:,c) = trapz(1:c,A(:,1:c),2);
end
B

trapz(x,y)